1. Field of the Invention
This invention relates to syringe systems for use in delivering fluids to a patient. More particularly, this invention relates to pressure syringe systems involving balloon-tipped catheters.
2. Background Art
Balloon-tipped catheter systems are frequently used in a variety of medical procedures such as urology, gynecology, cardiology and others. Particularly in connection with the treatment of coronary artery disease, the use of balloon-tipped catheters and their associated syringe systems have become widely used.
Coronary artery disease is the narrowing of the arteries that feed oxygen-rich blood to the heart. When the coronary arteries, which are located at the top of the heart and through which oxygenated blood is returned to the heart become narrowed or blocked, angina can result. Angina is a symptom of coronary artery disease characterized by chest pain or pressure that can radiate to the arm or jaw, and is caused by a lack of oxygen-rich blood to the heart muscle. Coronary artery disease results from atherosclerosis which is a build up of waxy material called plaque inside the arteries. When this happens, under exertion or stress the heart demands more oxygen, but the narrowed coronary arteries cannot supply enough oxygen-rich blood to meet the demand, resulting in angina.
One method for treating coronary artery disease is balloon coronary angioplasty, or more technically, percutaneous transluminal coronary angioplasty (PTCA). In performing PTCA, an introducer sheath is inserted through an incision made in the groin or in the artery of an arm. An X-ray sensitive dye is injected into the coronary artery through a catheter that is introduced through the sheath. The dye enables the doctor, through the use of real time X-ray techniques, to clearly view the arteries on a television monitor and to thereby locate the artery blockage. A balloon-tipped catheter is then advanced through the artery to the point of the blockage with the help of the X-ray monitor.
The balloon catheter is advanced to the middle of the blockage. The catheter, which is filled with a fluid and is coupled at its proximal end to a control syringe, is manipulated by the cardiologist. Once the balloon catheter is in place, the balloon is typically inflated for 20 to 60 seconds utilizing the control syringe. The balloon is then deflated and this procedure is repeated several times to compress the plaque on the arterial wall and thereby restore patency to artery. After the results are checked, the balloon catheter and guide wire are then removed.
Exacting control with respect to duration of the inflation periods is essential to the safety of the patient. When the balloon catheter is completely inflated so as to begin compressing the plaque, blood flow along the artery and then to the heart is thereby temporarily shut off. This creates the potential for initiating cardiac arrest or tissue damage due to oxygen deprivation. Accordingly, the duration of the blockage created by inflating the balloon catheter must both be carefully controlled by the attending cardiologist and other personnel. The duration of each inflation must be based on the cardiologist's assessment of the health of the patient and the patient's ability to withstand a temporary stoppage of blood flow to the heart during the inflation procedure.
It is also important to control the inflation pressure in order to insure adequate inflation to effect compression of the plaque, while avoiding over-inflation that can damage the delicate arterial wall tissue.
Obtaining an exact pressure can be difficult and time consuming with many syringe systems in use today. In order to increase the pressure even a small amount, the surgeon or other medical personnel must grasp the body of the syringe in one hand and the plunger in the other and carefully advance the plunger only a small amount in order to obtain the appropriate degree of catheter balloon inflation. This careful adjustment process is difficult and time-consuming, thereby distracting the surgeon from other important matters. The problem is exacerbated by the need to conduct successive cycles of inflation and deflation during a typical procedure.